Neck inspiratory muscle activation patterns during well-controlled inspiration

Area of Science:

• Respiratory Physiology
• Biomechanics
• Muscle Electromyography

Background:

• Neck inspiratory muscles play a role in breathing.
• Their activation patterns relative to mechanical parameters are not well understood.
• Previous assumptions may have underestimated the role of muscles like the sternocleidomastoid (SCM).

Purpose of the Study:

• To investigate the activation patterns of neck inspiratory muscles.
• To correlate muscle activation with controlled inspiratory flow rate and lung volume.
• To experimentally determine the relationship between muscle electromyography (EMG) and mechanical parameters.

Main Methods:

• Thirteen healthy subjects performed inspiratory maneuvers.
• Surface electromyography (EMG) of sternocleidomastoid (SCM) and scalene muscles was recorded.
• EMG amplitudes were analyzed against varying percentages of peak flow rate (%PFR) and forced vital capacity (FVC).

Main Results:

• Neck inspiratory muscle EMG increased exponentially with increasing %PFR.
• Muscle recruitment onset increased with increasing %FVC.
• A positive linear relationship was observed between %FVC and EMG, with a positive y-intercept at higher %PFR.

Conclusions:

• Neck inspiratory muscle activity is dependent on both airflow and lung volume.
• The sternocleidomastoid (SCM) muscle demonstrates consistent activation, even at low lung volumes.
• This challenges the traditional view of SCM as purely an accessory muscle.